There is known a catalytic converter which has a catalyst support made of an electrically-conductive material such as metal or silicon carbide (SiC) and supports a catalyst. In the catalytic converter, the catalyst is warmed up by heat which is produced when the electric current is applied to the catalyst support. In such catalytic converter, a case which houses the catalyst support and the catalyst support are insulated with each other so that the case and the catalyst support do not short-circuit. For example, there is known a catalytic converter which is housed and held in a cylindrical case via a mat covering an outer circumference of a metallic catalyst support, the mat being made of a ceramic material which is consisted primarily of ceramic fiber or the like (see patent literature 1). In addition, there are Patent Literatures 2, 3 as prior art references in relation to the present invention.